James M. Clark

James M. Clark

Ronald Weintraub Professor of Biology
Lisner Hall 346
Mobile: 202-994-7144


Systematics and Paleontology of Dinosaurs and Crocodylomorpha.

Current Research

My research addresses the interpretation of fossil land vertebrates (tetrapods), especially those from fossil deposits of the Age of Dinosaurs (the Mesozoic). My field work includes participation in the American Museum of Natural History-Mongolian Academy of Sciences expeditions to the Gobi Desert of Mongolia from 1991 to 2002 (at times as co-field leader), and extensive work in Mexico. My current NSF-funded field project is an exploration of the Middle to Late Jurassic Shishugou Formation of Xinjiang, China, in collaboration with Dr. Xu Xing of the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing. Research projects focus upon the evolutionary relationships of birds to theropod dinosaurs, based upon the collections from the Gobi Desert of Mongolia and China, and the function of the foot of pterosaurs based upon a new specimen from the Early Jurassic of Mexico. Check out the latest news from China.

Dinosaurs and the Origin of Birds

The theropod dinosaurs and primitive birds collected by the AMNH-MAS expeditions to the Gobi Desert include numerous skeletons providing important new information on the relationships of birds to other dinosaurs. Among these are the first embryonic dinosaur skeleton from Mongolia and specimens of oviraptors sitting on nests in a bird-like position. My NSF-funded research, in collaboration with M. Norell, L. Chiappe, and P. Makovicky, focuses on the relationships among the closest relatives of birds, especially oviraptorids, dromaeosaurids, troodontids, the bizarre therizinosaurs, and the unusual basal bird Mononykus. Supported by a $3 million NSF Tree of Life grant in 2002 (along with J. Cracraft, G. Barrowclough, and S. Hackett), we are now developing an online database of theropod and bird morphological characters including images of each character.

Locomotion in Pterosaurs

An exquisite skeleton of a primitive pterosaur from Huizachal Canyon in Mexico provides important information about the capacity for walking and running in these animals. In particular, the joint at the base of the toes (the metatarsal-phalangeal joints) are nearly flat, preventing them from bending back into a posture in which the animal walked or ran on its toes, rather than on the ball of its foot. This research is in collaboration with James Hopson of the University of Chicago.


Abundant isolated bones and articulated skulls of this obscure group of lizard-like reptiles distantly related to dinosaurs were collected in Nevada and are currently being removed from their limestone matrix in acid baths. This work is in collaboration with Hans-Dieter Sues of the Royal Ontario Museum and Nick Hotton of the National Museum of Natural History and funded by the National Geographic Society.

Phylogeny of Crocodylomorpha

My dissertation work on crocodylomorph phylogeny identified the major clades in this large group, which includes living crocodylians and a wide variety of extinct forms related more or less distantly to them. Clark (1994) presented a cladogram and data matrix for the Crocodyliformes, and Clark et al. (2000) presented an analysis of the remaining crocodylomorphs.

Phylogenetic Studies of Fossils

Fossils offer important information about evolutionary relationships, but they also are difficult to study because of they are invariably incomplete. My research explores the limitations and advantages of information from fossils, especially regarding the effect of missing data and the inference of non-morphological features of fossils.

Field Work

My field research, undertaken nearly every summer since my co-discovery of the Fruita Paleontological Area in the Late Jurassic of Colorado with George Callison in 1975, has focused on fossil vertebrates in dinosaur-age deposits (i.e., the Mesozoic). Two areas of special interest are the Cretaceous dinosaur deposits of Mongolia, as a member and co-organizer of the American Museum of Natural History-Mongolian Academy of Sciences expeditions to the Gobi Desert since 1991, and an Early Jurassic locality in the Sierra Madre Oriental of Mexico I discovered in 1982 with R. Cifelli, in Huizachal Canyon. Other field work includes expeditions to Late Triassic marine deposits of Nevada (with H.-D. Sues and N. Hotton), Early Jurassic fluvial deposits of the Glen Canyon Group in Arizona (with D. Fastovsky and K. Padian), Early Jurassic deposits in southern Arizona, Cretaceous-Tertiary boundary deposits of eastern Montana (with W. Clemens), Early Cretaceous deposits of central Mexico (with R. Hernandez and M. Montellano), Jurassic deposits of Venezuela (with M. Sanchez-Villagra), Tertiary deposits of Yemen (with I. Tattersall and P. Whybrow), and Cenozoic deposits of Vietnam (with I. Tattersall and J. Schwartz).

In 2000 I began a new field project in Middle to Late Jurassic deposits of Xinjiang, northwestern China along with Dr. Xu Xing. Organized in collaboration with the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, this project is directed towards discovering the earliest members of dinosaur lineages dominating the Cretaceous Period, including the theropod dinosaurs most closely related to birds.


A.B., University of California, Berkeley, 1978
M.S., University of California, Berkeley, 1985
Ph.D., University of Chicago, 1986
Post-Doctoral Work: Zoology Department, U.C. Davis (1987-1989), National Museum of Natural History (1989-1991), American Museum of Natural History (1991-1994)


Kearney, M. and J. Clark. 2003 Problems due to missing data in phylogenetic analyses including fossils: a critical review. Journal of Vertebrate Paleontology 23: 263-274.

Clark, J.M., X. Xu, C.A. Forster, and Y. Wang. 2004. A Middle Jurassic ‘sphenosuchian’ from China and the origin of the crocodylian skull. Nature 430: 1021-1023.

Pol, D., S. Ji, J. Clark, and L Chiappe. 2004. Basal crocodyliforms from the Early Cretaceous Tugulu Group (Xinjiang Province, China), and the phylogenetic position of EdentosuchusCretaceous Research 25(4): 603-622.

Göhlich, U.B., L.M. Chiappe, J.M. Clark, and H.-D. Sues.  2005. The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia). Canadian Journal of Earth Sciences 42: 307-321.

Kirkland, J.M. L.E.  Zanno, S.D. Sampson, J.M. Clark, and D. Deblieux. 2005. A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature 435: 84-87.

Xu, X. J.M. Clark, C.A. Forster, M.A. Norell, G.M. Erickson, D.A. Eberth, C. Jia, Q. Zhao. 2006. A basal tyrannosauroid dinosaur from the Late Jurassic of China. Nature 439: 715-718.

Xu, X., C.A. Forster, J.M. Clark, and J. Mo 2006. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China. Proceedings of the Royal Society of London (B) 273(1598): 2135-2140.

Norell, M.A. J. M. Clark, A.H. Turner, P.J. Makovicky, R. Barsbold, and T. Rowe. 2007. A new dromaeosaurid theropod from Ukhaa Tolgod (Ömnögov, Mongolia). American Museum Novitates, 3545, 51 pp.

Jia, C., Forster, C.A. and Clark, J.M. 2007. The first stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic Shishugou Formation of Xinjiang, China. Acta Geologica Sinica 81(3): 351-356.

Hu, Y.-M. Meng, J. and Clark, J.M. 2007. A new Late Jurassic docodont (Mammalia) from northeastern Xinjiang, China. Vertebrata Palasiatica 45(3): 173-194.

Attila, O, J. Clark, and D. Weishampel. 2007. First report on a new basal eusuchian crocodyliform with multicusped teeth from the Upper Cretaceous (Santonian) of Hungary. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 243(2): 169-177.

Xu, X. and J. Clark  2008. The presence of a gigantic theropod in the Jurassic Shishugou Formation, Junggar Basin, western China. Vertebrata Palasiatica 46(2): 157-160.

Montellano, M., J.A. Hopson, and J. Clark  2008. Late Early Jurassic mammaliaforms from Huizachal Canyon, Tamaulipas, Mexico. Journal of Vertebrate Paleontology 28(4):1130-1143.

Barrett, P.M., R.J. Butler, F.E. Novas, S.C. Moore-Fay, J.M. Moody, J.M. Clark, W, and M.R. Sanchez-Villagra, Z. 2008. Dinosaur remains from the La Quinta Formation (Lower or Middle Jurassic) of the Venezuelan Andes. Palaeontologische Zeitschrift 82(2): 163-177.

Xu, X., J. Clark, J. Mo, J. Choiniere, C.A. Forster, G.M. Erickson, D.W.E. Hone, C. Sullivan, D.A. Eberth, S. Nesbitt, Q. Zhao, R. Hernandez, C.-k Jia, F-l. Han and Y. Guo.  2009. A Jurassic ceratosaur from China helps clarify avian digital homologies. Nature 459: 940-944.

Norell, M.A., P.J. Makovicky, G.S. Bever, A.M. Balanoff, J.M. Clark, R. Barsbold, and T. Rowe. 2009. A review of the Mongolian Cretaceous dinosaur Saurornithoides (Troodontidae: Theropoda). American Museum Novitates 3654: 1-63.

Hu, Y., J. Meng, and J. Clark, 2009. A new tritylodontid from the Upper Jurassic of Xinjiang, China. Acta Paleontologia Polonica 54: 385-391.

Andres, B., J. Clark, and X. Xu 2010. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs. Journal of Vertebrate Paleontology 30(1): 163-187.

Choiniere, J., X. Xu, J. Clark,C.A. Forster, G. Yu, and H. Fanlu. 2010. A basal alvarezsaurid theropod from the early Late Jurassic of Xinjiang, China.  Science.327: 571-574.

Eberth, D.A., X. Xu, and J.M. Clark. 2010. Dinosaur death pits from the Jurassic of China. Palaios 25: 112-125.

Xu, X., J. Choiniere, M. Pittman, Q. Tan, D. Xiao, Z. Li, L. Tan, J. M. Clark, M. A. Norell, D. W. E. Hone and C. Sullivan. 2010. A new dromaeosaurid (Dinosauria: Theropoda) from the Upper Cretaceous Wulansuhai Formation of Inner Mongolia, China. Zootaxa 2403: 1-9.

Choiniere, J., J. Clark, X. Xu, and C. Forster. 2010. A basal coelurosaur (Dinosauria: Theropoda) from the Shishugou formation in Wucaiwan, People’s Republic of China. Journal of Vertebrate Paleontology 30: 1773–1796.

Han, F.l., J.M. Clark, X. Xu, C. Sullivan, J. Choiniere, and D. Hone.  2011. Theropod teeth from the Middle-Upper Jurassic Shishugou Formation of northwest Xinjiang, China. Journal of Vertebrate Paleontology 31: 111-126.

Clark, J.M. In press. A new shartegosuchid crocodyliform from the upper Jurassic Morrison Formation of western Colorado. Zoological Journal of the Linnean Society.

Classes Taught

BISC 6207 - Current Topics in Systematic Biology
BISC 6215 - Vertebrate Phylogeny
BISC 6216 - Morphological Systematics